Device for basting in lock-stitch sewing machines



June 3, 1969 l. RENDAHL 3,447,497

DEVICE FOR BASTING IN LOCK-STITCH SEWING MACHINES Filed May 26, 1966 United States Patent Office 3,447,497 Patented June 3, 1969 3,447,497 DEVICE FOR BASTING IN LOCK-STITCH SEWING MACHINES Ingvar Rentlahl, Huskvarna, Sweden, assignor to Husqvarna Vapenfabriks Aktiebolag, Huskvarna, Sweden Filed May 26, 1966, Ser. No. 553,070 Int. Cl. DOSb 3/02 U.S. Cl. 112158 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to sewing machines, particularly for households, comprising a substantially horizontal work-support, a reciprocating work-feeder associated therewith, a longitudinally reciprocating sewing needle and a loop-taker situated below the work-support and cooperating with the needle to form lock-stitches.

The invention has for its object to provide such machines with a simple and reliable device which can readily be switched on for producing a straight seam of lockstitches much longer than the maximum throw of the work-feeder which seam can be used to advantage for basting.

With this object in view the invention comprises the novel combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawing. The advantages attained thereby will be readily understood by those skilled in the art.

The invention will be particularly described in the following with reference to the annexed drawing wherein FIG. 1 schematically shows a zigzag sewing machine to which the invention is applied. FIG. 2 is a partial front view of the loop-taker and adjacent parts of the machine. FIGS. 3 and 4 are sections on lines 33 and 44 in FIG. 2 respectively. FIGS. 5 and 6 show two seams. FIG. 7 is a front view corresponding to FIG. 2 of a second embodiment of the invention.

The machine shown comprises a hollow casing 5 with a work-support 6 including a stitch plate, a bearing 8 for a needle-bar 9 with needle 10, the bearing being swingable on a pivot 7 in the casing, a drive shaft 11 with crank driving device 12 for the longitudinal motion of the needle-bar, a cam shaft 13 crossing shaft 11 p rpendicularly and carrying a cam disk 14 driven from shaft 11 by means of a worm gear 15 with the gear ratio 18:1, a cam follower 16 swingable in the plane of cam disk 14 about a pivot 17 on a lever 18 with a stationary fulcrum 19, a link 20 connected to the lever 18, guided by a pin 21 and spring-operated against a manually settable cam disk 22 for changing the stitch field, and a link 23 connected at one end with the needle-bar bearing 8, its other end 24 being in contact with the rear side of cam follower 16 and, for changing the stitch Width (the amplitude of transversal needle motion) between zero and a maximum value, say 4 mm., adjustable along the cam follower by means of a manually settable cam disk 26, a lever 27 spring-operated against said cam disk, and a link 28. A lower work-feeder 29 with a substantially rectangular path of movement is driven horizontally by an eccentric 30 on drive shaft 11 by means of a rock shaft 31 and a forked rod 32 with a die 33 engaging a manually turnable feed control guide 34 for regulating the stitch length between zero and the maximum value, say 4 mm.

Driven from shaft 11 is also a loop-taker or shuttle 35 designed according to Patent 2,851,978 and thus having a circumferential flange 36 with hook 37 supported between a stationary, annular cover or retainer 38 and a concave driving member 51 for the loop-taker which for each stitch makes two revolutions in the clockwise direction in FIGS. 1 and 2 about a transversal, horizontal axis 39 and contains a nonrotating spool case 40 which can be taken out from in front through a casing-opening in the casing after opening a lid not shown here which lid, in machines having a cantilevered work-supporting arm, can be arranged to be swung down in front of the loop-taker and, in so-called flat-table machines, can be a retractable slide plate forming part of the work-support 6. The cover 38 has a recess 41 for the needle 10. This one and the book 37 are shown in FIG. 2 at loop-taking in the lateral end positions of the needle 10 at maximum stitch width. The machine also comprises an upper-thread regulating arm not shown, driven from shaft 11, and an adjustable upper-thread tightening spring operative at the descending movement of the needle. So far the machine can be of known design which need not be more closely described.

In the embodiment shown in FIGS. 2-4 a thin, say 0.2 mm. thick sheet metal slide 42 having a tongue 43 is countersunk and horizontally guided on the rear side of the cover 38 which has a slot 44 for a shank 45, penetrating the slide, of a handle 46 accessible through the above mentioned casing-opening for the removal of spool case 40. Parts 42 and 46 are held against the cover 38 by a pressure spring 47 confined between the slide and shank 45. By means of handle 46 the slide 42 is slidable between two end positions A, B indicated in FIG. 2 by the center line of the handle and determined by contact between the shank 45 and the ends of slot 44. In operative position A, tongue 43 is situated between the movement path of the hook and the left vertical movement path of the needle and thereby prevents loop-taking and stitch forming in the left end position of the needle, not in the right one. In order surely to prevent the needle when moving downwards from striking the tongue 43, the latter has along its upper edge a part 48 diverging upwardly from the movement path of the needle. In position B the tongue is inoperative out of said paths of movement. In

FIG. 4 the upper-thread is denoted by 49.

In FIGS. 5 and 6 the full lines indicate the upperthread and circles C, D the points Where the needle stitches in the fabric. The shape of cam disk 14 is such, that the needle after each stitch C in its right end position makes 5 stitches D in its left end position. If member 34 is set for maximum stitch length, member 26 for maximum stitch width (the setting of member 22 being then insignificant) and slide 42 in operative position A, no stitch formation occurs at the stitch points D, a straight seam according to FIG. 6 being obtained wherein the stitch length is six times the normal maximum one which seam can "be used to advantage for basting. If the tongue in position A reaches the central needle position, the stit h width can also be less than the maximum one. If, on the other hand, slide 42 is held in position B, stitch formation occurs also at the points D and a seam according to FIG. 5 is obtained which, preferably with another setting of members 26 and 34, can be used for hemming.

The cam disk 14 can in known manner be exchangeable for others or be one of a plurality of cam disks selectively connectible with cam follower 16. Cam disk 14 can preferably also be shaped so as to hold the needle in its right lateral position during a plurality of stitches after each stitch in its left lateral position, the separating member 43 being then arranged oppositely and to the right so as to prevent stitch formation in the right lateral position.

The invention can also be applied to prevent stitch formation in one lateral position of an ordinary straight zigzag seam and thus to obtain a straight seam with twice the stitch length set. At least in this application the upperthread tension should be means of the above mentioned thread tensioning device, be so reduced that the upperthread and the under-thread interlock at the underside of the fabric so that the under-thread can be readily drawn out in spite of the relatively small stitch length.

The embodiment according to FIG. 7 differs from that according to FIGS. 1-4 only as to the mounting and movement of the separating member, a sheet metal tongue 52 similar to tongue 43. In FIG. 7 loop-taker cover 38 is omitted and only indicated in dot-and-dash lines. Reference numeral 50 denotes a vertically movable workfeeder carrying arm. Tongue 52 is rigidly connected with an arm 54 swingable behind driving member 51 on a fixed pivot 53 and having a cam follower 55 urged by a spring 56 against a cam disk 57 mounted on a ca m shaft journalled in the casing. The cam disk 57 has five equidistant cams 58, intermediate depressions 59 and is turned by a driving device in the shape of a sprocket wheel 60, a feed pawl 62 pivoted on arm 50 and actuated by a spring 61, and an arresting pawl 64 swingable on pivot 53 and actuated by a spring 63. A control member 65 corresponding to the control means 45, 46, horizontally slidable on cover 38 and carrying a rearwardly directed pin 66 is manually settable from the outside into positions a, b denoted in FIG. 7 by the center line of slide member 65. In position b pin 66 is in contact with a finger 67 on arm 54 and holds the latter raised from cam disk 57. In position a pin 66 is out of the movement path of the finger determined by the cam disk 57.

During normal sewing tongue 52 is kept in inoperative position by slide 65 in position b. For basting, the slide is set in position a and needle is set for straight stitching in the left starting position. The shape and the drive motion of cam disk 57 are such that tongue 52. is now alternately held in the operative position shown wherein it prevents stitch formation, during five consecutive loop-taking motions of hook 37, and (by earns 58) in an inoperative position to the left of the operative position during the subsequent loop-taking motion, there being thus obtained a straight seam of lock stitches having a stitch length six times the one, say 4 mm., for which the work-feeder 29 is set by means of the ordinary feed control member 34 of the machine.

The separating member can, for instance, also be a thin tube-piece insertable closely beside or above the movement path of the hook so as to be penetrated by the needle. An automatically movable separating member can also be used in straight stitch sewing machines and can be driven also from an oscillating loop-taker or, via some suitable transmission, from a rotary loop-taker shaft or work-feed shaft. In connection with loop-takers without stationary cover 38 the separating member can be mounted, optionally swingably, on some other stationary part of the sewing machine, optionally on the underside of the stitch plate.

What I claim is:

1. In a lock-stitch sewing machine comprising a casing including a work-support, a reciprocating work feeder associated with said work-support, a longitudinally reciproeating sewing needle, a loop-taker situated below said work-support, cooperating with said needle to produce lock stitches and having a hook movable past said needle in the course of loop-taking, drive shaft means for each of said needle, work-feeder and loop-taker, a basting de- Vice comprising a separating member mounted below said work-support and reciprocably movable between an inoperative position and an operative position close to the position of the needle and hook at loop-taking and adapted in its operative position to keep the needle thread from said hook and thereby prevent loop-taking, control means associated with said separating member and capable of being set manually from outside said casing so as to keep said separating member inoperative, a driving device movable in timed relation to the loop-taker and adapted to hold the separating member alternately in its inoperative position during a loop-taking motion of said hook and in operative position during a number of such hook motions and said control means being capable of disconnecting said separating member in its inoperative position from said driving device.

2. A device as claimed in claim 1 in which said driving device comprises a cam disk making one revolution during a plurality of loop-taking motions of said hook, a cam follower operatively connected with said separating member and spring means for urging said cam follower towards said cam disk.

3. In a lock-stitch sewing machine comprising a casing including a work-support, a reciprocating work-feeder associated with said work-support, a longitudinally reciprocating sewing needle, a'loop-taker situated below said work support, cooperating with said needle to produce lock stitches and having a hook movable past said needle in the course of loop-taking, and drive shafts for said needle, work-feeder and loop-taker, a basting device comprising a separating member mounted below said worksupport, reciprocable between an inoperative and an operative position close to the position of said needle and hook at loop-taking and adapted in its operative position to keep the needle-thread from said hook and thereby prevent loop-taking, a driving device for reciprocably moving said separating member between the operative and the inoperative positions, comprising a cam shaft, cam control means journalled on said cam shaft, motion transferring members interconnecting said cam control means and one of said drive shafts for rotating said cam control means in timed relation to said loop-taker and said driving device being adapted to hold said separating member in its operative position during a plurality of stitches and after those stitches intermittently in its inoperative position.

4. A sewing machine according to claim 3 wherein said cam control means comprises a cam disk, a cam follower operatively connected with the separating member and spring means for urging said cam follower towards said cam disk and said motion transferring means comprises a ratchet attached to said cam disk and a pawl pivoted on said work-feeder and cooperating with said ratchet.

References Cited UNITED STATES PATENTS 434,996 8/ 1890 Sawtell 112-227 479,369 7/1892 Kern 112-164 898,403 9/ 1908 Corey 112-227 3,113,536 12/1963 Perla 112-158 3,115,110 12/1963 Ketterer 112-181 3,361,100 1/1968 Bono 112-158 3,374,754 3/1968 Gianinazzi 112-158 JAMES R. BOLER, Primary Examiner.

U.S. Cl. X.R. 112-187, 201 

